As is known in the art, pulse-width modulated (PWM) inverters are conventionally employed for DC/AC (direct current/alternating current) power conversion applications. If an application requires galvanic isolation and/or voltage transformation, an isolated, high frequency DC/DC converter is conventionally added as inverter front end. Two power conversion stages along with extra DC link energy storage components result in significantly increased size and weight of such systems. Other drawbacks of conventional systems are low efficiency and high EMI emissions typical for hard-commutated PWM inverters.
Various embodiments of quasi-single-stage, high-frequency link, single-phase inverters have attempted to overcome the drawbacks of conventional, two-stage systems. These quasi-single-stage inverters utilize an isolated DC/DC converter to generate a sine wave modulated DC output voltage or current. The modulated DC waveform is then converted into AC by a low frequency unfolding inverter. By eliminating large DC link energy storage components and high-frequency switching in the unfolding inverter significant improvements in weight, size, efficiency, and EMI can be achieved. However, three-phase implementation of known quasi-single-stage, high-frequency link inverters is much less advantageous, since it requires three isolated DC/DC converters and three single-phase unfolding inverters.